1. Field of the Invention
The present invention relates to a gasket of rubber or a similar material for sealing joints between the sealing surfaces of two members to be joined, for example pipe sections comprising a spigot and a socket part, the gasket being placed in a fixed position on the sealing surface of one of the members and the sealing surfaces of the members being displaced substantially parallel to each other for squeezing the gasket therebetween due to displacement of portions of the gasket relative to other gasket portions.
2. Statement of the Prior Art
When joining basin rings and similar members having a spigot and a socket end rolling sealing rings are extensively used. During the joining of the members the sealing rings roll along substantially coaxial sealing surfaces and are compressed therebetween.
A disadvantage in connection with this sealing method consists in that the rolling sealing rings may roll non-uniformly during the joining operation, which implies that the ring may take an oblique position in the sealing area when the joining operation has been completed. Such an oblique position of the rolling sealing gasket may result in a leakage in the joint area.
To remedy this difficulty there have been manufactured gaskets which are placed in their final position on the spigot end of a first member. Subsequent to the positioning of the gasket on the first member the socket end of the next member on which a lubrication means has been applied, is pushed onto the spigot end of the first member and thereby onto the gasket thereof, the sealing surface of the socket end sliding along the gasket to its final position.
However, this sealing method is encumbered with the problem that in order to reduce the friction between the gasket and the member the external sliding surfaces must be provided with substantial amounts of a suitable lubrication means. This is especially true in connection with concrete products, the sliding surfaces of the socket end being non-uniform and rough, so that relatively large pores and cavities must be filled with the lubrication means. However, on the installation site the surfaces covered with the lubrication means may easily attract dust and sand particles, a fact which contributes to a reduction of the sliding properties and may cause damage to the gaskets. Further, the lubrication means may easily be washed away subsequent to the installation with leakage as a result. Besides, due to the tolerances which are unavoidable in connection with concrete pipes the socket parts may easily break as a consequence of too high a gasket pressure.
From U.S. Pat. No. 3,510,140 there is known an annular gasket having a V-shaped cross section, one leg of which is adapted to be placed around the spigot end of a first pipe. The free end of the other leg is bead-shaped, and between the two legs there is defined a wedge-shaped pocket adapted to hold a lubrication or sliding means. Whilst mounting the socket end of a second pipe on the spigot end of the first pipe the socket end will push the outer leg of the gasket to its final sealing position, the lubrication means facilitating the displacement between the gasket parts.
Such a gasket will solve the problem of exposed sliding surface portions and contribute to a comparatively easy installation of the parts to be joined. However, the installed parts may also easily be taken apart since the gasket scarcely offers larger resistance when the jointing members are subjected to forces seeking to force them apart.
From U.S. Pat. No. 2,032,492 there are known pipe joint assemblies comprising a rubber sealing ring having at its radially inner and outer faces a plurality of circumferentially extending ridges and circumferentially extending apertures formed in the rubber body. The ridges are flexed in the proper axial direction by which the resistance to the assembly movement is the lesser, and their resistance to pipe movement in the opposite axial direction is the greater by virtue of their tendency under the frictional drag to be swung more tightly against the pipe wall. However, this known sealing ring can only be used in connection with pipes of comparatively weak material, such as terra cotta or other ceramic material, the grooves between the ridges being sufficiently wide to permit considerable flexure of the ridges and each ridge preferably being generously wide at its base so as to make available ample resilience of the rubber for effectively sealing by flexure of the ridges, but without such radial compression of the ring body as might set up a pressure too great for the fragile material of the pipes.
According to this patent specification it is desirable to have a gasket which is very softly resilient so as to be adaptable effectively to annular spaces of varying radial depths. To increase the softness of the rubber sealing ring this is provided with circumferentially extending apertures formed in the rubber body as the zones where it would otherwise present the greatest resistance to radial compression, that is to say in the zones of the ridges. In other words U.S. Pat. No. 2,032,492 gives directions for a gasket which easily may have its cross section altered, the joining force between the pipe ends to be assembled being provided by external circumferentially extending flanges.
However, the reduction of the cross section which is provided by the gasket according to U.S. Pat. No. 2,032,492 is brought about by the material between the passages or the apertures being forced thereinto whilst the gasket material is subjected to bending. Because the gasket material is bent, it will have a poor sealing effect since the force from a bent elastic portion far from gives the same sealing effect as the force from a portion which is only clenched together without being bent. Accordingly, the known gasket will give a poor sealing effect at higher pressures, and the bent soft and elastic flanges on the outside of the gasket will at least in the embodiment illustrated in FIG. 10, hardly change this unfavourable condition. In the embodiment illustrated in FIGS. 4 and 5 of this Patent Specification the above adverse condition is somewhat improved, but this embodiment is limited to having the gasket mounted in a socket section prior to the pushing of a pipe spigot end thereinto.
In U.S. Pat. No. 3,575,430 there is disclosed a packing ring having an irregular cross section profile and being provided with a series of passages which are open in unmounted condition of the ring, but which during installation are closed by compression, the ring material then being sent into the passages whilst forming S-shaped curves. However, the function of the passages in the ring material is to provide a compression of the ring in an inner track in a sleeve which embraces the two spigot ends of two pipes to be jointed, and to obtain a further compression of the body of the ring the ring body is further cut away at one edge so that this edge of the ring is formed with a curved surface providing more space within the annular channel of the socket part to accommodate ring compression.